Solid composition

ABSTRACT

A solid, water-soluble or water-dispersible composition comprising a non film-forming material (such as a water-soluble agrochemical) supported by a film-forming polymer is prepared by (i) preparing a film-forming aqueous medium containing (a) a film-forming polymer which is a partially or fully charged homopolymer or a partially charged block copolymer or a homopolymer or block copolymer capable of ring-opening to form a partially charged homopolymer or block copolymer and (b) a water soluble material which is non film-forming (such as a glyphosate salt) and thereafter (ii) drying the film-forming aqueous medium to form the solid composition. The preferred film-forming polymer is alkyl vinylether maleic anhydride block co-polymer or a hydrolysed form thereof.

This invention relates to a solid composition and to a process forpreparing a solid composition and in particular to a process forpreparing a solid, water-soluble or water-dispersible compositioncontaining a water-soluble material which is not film-forming and afilm-forming water soluble material.

Film-forming polymers are used in a number of industries to provide asolid polymer medium within which a second non film-forming componentmay be supported. Typical of such applications is the casting of anaqueous solution of the film-forming polymer to form polymer sheets(tapes) or flakes.

Thus for example in WO 93/23999 there is disclosed a packaging forstoring and releasing incompatible crop protection materials in which achemical is “encapsulated” or supported in a water-soluble polymer film.

Such processes typically involve as a first step dissolving afilm-forming polymer in water to form an aqueous film-forming medium inwhich a material to be supported is dissolved or suspended. Thefilm-forming medium is then for example cast onto a suitable substrateand dried to form a solid tape containing the material to be supported.Under certain conditions the tape may loose coherence during drying toform flakes. Alternatively, the film-forming medium can be dried toproduce granules, agglomerates or powders.

We have found however that problems may arise when the non film-formingmaterial to be supported is itself water-soluble, particularly if it isa strong electrolyte. Specifically, we have found that the presence of awater-soluble electrolyte in an aqueous solution of a conventionalfilm-forming polymer tends to interact adversely with the polymer at therelatively high polymer concentration required to provide adequatefilm-forming properties. As a result the film-forming polymer may bethrown out of solution as a rubbery deposit, and even quite smallconcentrations of water-soluble electrolyte may have a deleteriouseffect on the film-forming properties and homogeneity of the medium. Theproblem is exacerbated if the water-soluble electrolyte is hygroscopicsuch that even if a solid composition can be formed, it tends to pick upwater causing the film-forming polymer component to become sticky.

In our co-pending United Kingdom Patent Application No 9810861.6 thereis described a process for producing a solid, water-soluble orwater-dispersible composition comprising a non film-forming materialsupported by a film-forming polymer wherein the supported material is awater-soluble material, which process comprises (i) preparing afilm-forming aqueous medium containing (a) a film-forming polymer (b) awater soluble material which is non film-forming and (c) awater-miscible solvent in which the film-forming polymer is soluble andthereafter (ii) drying the film-forming aqueous medium to form the solidcomposition. We have now found a specific class of polymers which arecompatible even with a water soluble electrolyte and which do notrequire the use of a water-miscible solvent in which the film-formingpolymer is soluble. Those skilled in the art will appreciate thesignificant process advantages in being able to avoid the use of a watermiscible co-solvent such as an alcohol.

Thus according to the present invention there is provided a process forproducing a solid, water-soluble or water-dispersible compositioncomprising a non film-forming material supported by a film-formingpolymer wherein the supported material is a water-soluble material,which process comprises (i) preparing a film-forming aqueous mediumcontaining (a) a film-forming polymer which is a partially or fullycharged homopolymer or a partially charged block copolymer or ahomopolymer or block copolymer capable of ring-opening to form apartially charged homopolymer or block copolymer and (b) a water solublematerial which is non film-forming and thereafter (ii) drying thefilm-forming aqueous medium to form the solid composition.

Suitably the film-forming aqueous medium is prepared using water as thesole medium (solvent or dispersant) for both the film-forming polymer(a) and the water-soluble material (b), and in particular in thesubstantial absence of a water miscible solvent in which thefilm-forming polymer is soluble.

Whilst the process of the present invention may be applied to anywater-soluble material which is not film-forming and which is suitablefor being supported in a solid composition of a film-forming polymer, itis of particular relevance when the water-soluble supported material isa strong electrolyte and even more particularly when the water-solublesupported material, in its dry form, is hygroscopic. Typical strongelectrolytes are salts, for example salts of an organic acid or base.The scope of the present invention is not restricted to a water-solublesupported material having a specific utility, although it is illustratedherein with reference to a water-soluble supported material havingutility in the agrochemical field, either as an active agrochemical oras an agrochemical adjuvant. Typical examples of water-soluble activeagrochemicals which are strong electrolytes are salts of glyphosate,including without limitation the trimethylsulphonium salt, theisopropylamine salt, the sodium salt, the potassium salt and theammonium salt and bipyridylium salts such as paraquat dichloride ordiquat dibromide, glufosinate and fomesafen.

Typical examples of agrochemical adjuvants which are strong electrolytesare organic or inorganic salts such as ammonium sulphate. The process ofthe present invention provides a convenient method of obtaining a solidformulation of an agrochemical or an agrochemical adjuvant or anagrochemical formulation containing both active agrochemical andadjuvant having advantages in respect of handling, storage,transportation and reduced container contamination. Typical solidformulations of the present invention such as tapes or flakes provide aconvenient delivery vehicle for the agrochemical or agrochemicalformulation and may be arranged for example such that a single unit doseof agrochemical is contained in a unit dose package, for example in aconventional unit dose package or in water-soluble sachet packaging. Ifthe process of the present invention is used to form a cast tape, thetape may be cut to provide a length corresponding to a desired dose.Furthermore we have found that the process of the present invention maybe used to provide solid compositions containing a high loading ofagrochemical or agrochemical adjuvant and in many instances a higherloading than would be possible in the absence of water-miscible solventor with conventional water-soluble polymers. In certain circumstancesthe process of the present invention may be used to provide a solidcomposition containing an agrochemical formulation whose individualcomponents are incompatible or show long-term physical instability ifused in the form of an aqueous liquid concentrate. Thus for example itmay be possible to use a higher content of an adjuvant such as ammoniumsulphate than would be compatible as an aqueous liquid concentrateformulation of an agrochemical.

The term “film-forming” polymer indicates that the polymer is capable ofproviding film-forming properties in the presence of water. Thefilm-forming polymer will generally be at least partially water-solublebut could also provide a film-forming aqueous medium in which thefilm-forming polymer is present in the form of a dispersion, and inparticular a colloidal dispersion or in the form of a sol or latex or inthe form of a solution containing some dispersed material.Alternatively, as described below, an insoluble form of homopolymer orblockcopolymer may be converted to a soluble or partially soluble formunder the process conditions.

By the term “a partially or fully charged homopolymer or a partiallycharged block copolymer” is meant a homopolymer or block copolymerhaving anionic functional units such as carboxylic acid or sulphonicacid functional units or a mixture of such anionic functional unitsassociated with a suitable cation or cationic functional units such asan alkali or alkaline earth cation, for example a sodium cation. Ifdesired the charged, anionic, functional unit may be generated in situfor example by ring opening of an uncharged block co-polymer orhomopolymer.

An especially suitable block copolymer capable of ring opening to form apartially charged block copolymer is an alkyl vinylether maleicanhydride block copolymer which is capable of ring opening in water,particularly under basic conditions or in the presence of suitablespecies to form a dicarboxylic acid or its derivatives such as salts orpartial esters. Dicarboxylic acid derivatives of an alkyl vinyethermaleic anhydride blockcopolymer and their salts and partial esters arepreferred examples of a partially charged block copolymer.

The alkyl vinylether maleic anhydride block copolymer and its partiallycharged derivatives are preferably lower (C₁ to C₄) alkyl vinylethermaleic anhydride block copolymers for example methyl vinylether maleicanhydride block copolymers. Such copolymers are based on strictlyalternating copolymers of alkyl vinyl ether and maleic anhydride whichmay be combined to produce products of various molecular weights. Amethyl vinyether maleic anhydride block copolymer has the generalformula (I) in which the value of n indicates the molecular weight(degree of polymerisation).

In general the block copolymer will consist of a mixture havingdifferent degrees of polymerisation and n normally represents an averagevalue corresponding to an average molecular weight.

Methyl vinylether maleic anhydride block copolymer is essentiallyinsoluble in water but hydrolyses slowly to give the acid form. Thishydrolysis is more rapid under basic conditions or in the presence ofsuitable species, as illustrated in Reaction Scheme I.

As examples of fully or partially charged block co-polymers suitable foruse in the process of the present invention there may be mentioned saltsof co-polymers, such as the sodium salt of poly (acrylic acid/maleicacid) copolymer and salts such as the sodium salt of sulphonated poly(styrene/maleic anhydride) copolymer. As examples of partially or fullycharged homopolymers suitable for use in the process of the presentinvention there may be mentioned salts, for example alkali metal saltsof acidic homopolymers or of sulphonated homopolymers, for example thesodium salt of sulphonated polystyrene, the sodium salt of sulphonatedpolyvinyl alcohol, the sodium salt of polyacrylic acid and the sodiumsalt of polymethacrylic acid.

The process of the present invention is especially well suited to theproduction of a solid formulation of a glyphosate system and inparticular a glyphosate system containing an ammonium salt such asammonium sulphate as adjuvant. We have found that, surprisingly, thereis no need to include an inert filler in the composition if ammoniumsulphate is present in the preferred proportions. Whilst it is possibleto adjust the pH of the system by the addition of a suitable base, it isespecially convenient to employ a glyphosate system in which the pH isalready in the desired range. An especially suitable glyphosate systemis an ammonium glyphosate system and preferably an ammonium glyphosatesystem containing an ammonium salt such as ammonium sulphate. Whilst theammonium ion present in such a composition should not be thought of asbeing associated specifically with either the glyphosate anion or forexample the sulphate anion, it is convenient to express theconcentration of ammonium ion relative to glyphosate ion as being inaddition to that which may also be present in the “ammonium salt”. Thusthe molar ratio of ammonium ion (in excess of that in the “ammoniumsalt”) to glyphosate is preferably from 1:1 to 2:1, for example from1.7:1 to 1.9:1. These ratios correspond to a pH of from about 3.5 to 6.6and from about 5.7 to 6.2 respectively.

We have found that if solid, powdered methyl vinylether maleic anhydrideblock copolymer is added to an aqueous solution of ammonium ions andglyphosate ions at a ratio as indicated above, and the mixture isallowed to stand, for example for about 30 minutes, a clear solution isformed. It is believed that the methyl vinylether maleic anhydride blockcopolymer has undergone ring opening to the soluble dicarboxylic acidform. We have found that the solution is initially of relatively lowviscosity but that the viscosity increases on standing. Whatever thereason for the observed viscosity behaviour, this behaviour may be usedto advantage in process terms and there may therefore be a benefit inthe use of the unhydrolysed methyl vinylether maleic anhydride blockcopolymer as starting material as opposed to using the hydrolysedmaterial from the start. Thus whilst it is believed that the process ofthe present invention involves the solubilisation of an alkyl vinylethermaleic anhydride block copolymer via ring opening under alkalineconditions or in the presence of an suitable species such as thosepresent in solution of ammonium glyphosate, the scope of the presentinvention is not limited by any such theory. Regardless of the precisemechanism involved, it is observed that an alkyl vinylether maleicanhydride block copolymer is soluble for example in ammonium glyphosatesolutions used in the process of the present invention and forms astable film-forming medium. A preferred process according to theinvention is thus a process wherein the water-soluble material is a saltof glyphosate, the film-forming medium is an alkyl vinylether maleicanhydride co-polymer and there is incorporated in the film-formingmedium an ammonium salt, preferably in the substantial absence of aninert filler.

Thus according to a further aspect of the present invention there isprovided a process for producing a solid, water-soluble orwater-dispersible composition comprising a glyphosate herbicidesupported by a film-forming polymer which process comprises (i)preparing a film-forming aqueous medium containing (a) a film-formingpolymer which is an alkyl vinylether maleic anhydride block copolymer,(b) an ammonium salt of glyphosate and optionally (c) ammonium sulphateand (ii) drying the film-forming aqueous medium to form the solidcomposition.

If desired the film-forming aqueous medium formed in stage (i) may beallowed to stand until a clear solution is formed or until hydrolysationis substantially complete or until a desired viscosity increase takesplace. Preferably the ammonium sulphate is present in the substantialabsence of an inert filler.

It may be desirable to include a filler such as an inert inorganicfiller in the solid composition. As noted above, it is an unexpectedadvantage of the process of the present invention however that anammonium salt such as ammonium sulphate may be used both as adjuvant foran active material such as glyphosate and also as filler. If desiredhowever an inert filler may be used in addition to or instead ofammonium sulphate. The inert filler is preferably a water-dispersiblesolid inorganic or organic filler such as calcium silicate, magnesiumsilicate (talc), sodium aluminium silicate, silica, mica, cellulosicfibre such as wood fibre, starch and diatomaceous earth. It isespecially preferred that a highly adsorptive filler is used, forexample a filler having a high surface area for example a surface areagreater than 5 m²/g and preferably greater than 80 m²/g. Ultra-finefillers such as fumed silica are not generally satisfactory however. Asa specific example of a suitable filler there may be mentioned CALFLO E(CALFLO is a trade mark World Minerals), a calcium silicate fillerhaving a surface area of about 100 m²/g.

The film-forming aqueous medium is preferably formed by first dissolvingthe film-forming polymer in the relevant aqueous medium. Thus by way ofexample, a film-forming aqueous medium containing ammonium ionsglyphosate ions and sulphate ions may conveniently be prepared by thefollowing method:

-   -   1. Methyl vinylether maleic anhydride is added as a solid to an        aqueous solution containing ammonium ions and glyphosate ions        (for example containing about 40% by weight based on glyphosate        acid). On mixing and standing a colourless solution of        relatively low viscosity is formed.    -   2. To this solution is optionally added a surfactant if used        either to provide biological enhancement of the glyphosate or to        affect the surface tension properties of the film-forming        aqueous medium relative to a substrate on which it is cast.    -   3. The desired proportion of finely ground solid ammonium        sulphate is added next. In general the volume of water present        will not be sufficient to dissolve all the ammonium sulphate,        but since the ammonium sulphate is acting in part as inorganic        filler this does not represent a problem.

The above order of addition is not essential but is preferred since itensures that the methyl vinylether maleic anhydride copolymer is addedto an appropriate medium comprising a component to ensure hydrolysis(i.e. the ammonium glyphosate). The other components may be added whilstthe viscosity is relatively low, whilst if the viscosity increases onstanding it may have beneficial effects in terms of even dispersion ofany undissolved ammonium sulphate and in terms of film-formingproperties.

The resultant film-forming aqueous medium is then dried to form a solidcomposition. The physical form of the resultant solid composition willdepend on the exact manner of drying of the film-forming aqueous mediumand a wide variety of processes may be used to provide a wide range ofsolid products. For example simple drying of the film-forming aqueousmedium will generally form a powder or agglomerate. Greater control ofthe formation of a powder or granule product may be obtained by spraydrying or freeze drying of the film-forming aqueous medium. Thefilm-forming medium may be partially or wholly formed into fibres, forexample by being extruded into a fast-moving stream of air, and theresultant solid composition may take the form of fibres or of a uniformparticulate composition resulting from the breaking up of such fibres onfurther drying. The film forming aqueous medium can also be applied onan anti-adherent, rotating drum surface by means of a roller andsubsequently dried by hot air to yield dry flakes. Alternatively thefilm-forming material may be cast in the form of a film onto asubstrate, for example a conveyor belt, from which it is preferablyremoved after drying.

The casting of the film-forming aqueous medium onto a substrate may takeplace using conventional techniques such as tape casting. In tapecasting, a film is formed on a substrate and the thickness is adjustedto that required using a device such as a “doctor blade” which defines apre-determined space between the surface of the substrate and the knifeof the doctor blade. The substrate is conveniently a flat, planarsurface but may also if desired possess indentations to provideappropriate corresponding patterning on the surface on the film.Similarly, the “doctor blade” may have a contoured knife to providecorresponding patterning on the top surface of the film. In the extreme,the substrate may comprise one or more wells into which the film-formingaqueous medium is cast so that discrete pellets or tablets are formed ondrying.

In commercial practice, it is normal to supply the film-forming mediumfrom a reservoir and to form the film continuously, for example by theuse of a moving belt as substrate or by movement of a reservoir andassociated doctor blade relative to a stationary substrate. Incommercial practice it is usually convenient to use a metal substratealthough a plastics substrate may be used if desired.

The cast medium may be dried under atmospheric conditions but it is moreconveniently dried at elevated temperature. In general it is sufficientto dry the cast medium at a temperature of from ambient to 100° C., forexample from 40 to 60° C. It is to be understood that the drying processwill not necessarily remove all traces of water and of the solvent forthe film-forming polymer, and indeed a small proportion of residualwater or solvent in the dry, cast product may have a beneficialplasticising effect. Typically levels of water in the range of 0.1 to20% by weight are to be expected in the dry, cast product. Heating maybe achieved for example by passing the cast medium into an oven orheated space or by applying heat to the substrate. Once the cast mediumis dried, it may be removed from the substrate for subsequent use.

The cast medium may be removed from the substrate as a coherent sheet (acast tape) and the coherent sheet may if desired subsequently besubdivided, for example by cutting, punching, or flexing to form flakesor shaped forms. Alternatively the proportions of the components of thefilm-forming medium, for example the content of the solid filler, may beselected such that the cast medium looses coherency during drying andcracks with the formation of flat flakes of product.

The thickness of the cast product, for example the cast tape or flakes,may be varied within wide limits according to the desired application.Typically the thickness of a cast tape or flakes varies between about0.04 mm to 5 mm depending on the flexibility and other characteristicsdesired. If flakes are not formed directly, the dry tapes can be cut orfashioned to include a wide variety of shapes and designs, including forexample discs, flakes, strips, tubes and spirals. The tape can be cut toprovide a pre-determined metered dose of active ingredient whichsimplifies the formation of a dilute agrochemical spray for example. Thetapes may also be embossed, corrugated or patterned to increase thesurface area and may also carry printed information such as product andsafety information.

For certain applications it may be desirable to protect the surface ofthe cast, dry product. The surface of the cast product may readily beprotected by lamination or co-casting with a layer of water-solublepolymer which contains no active product and which may be the same as ordifferent from the film-forming polymer. Alternatively, the cast, dryproduct may be housed in a water-soluble bag which may be manufacturedfrom the same or different water-soluble polymer.

The proportions of the components of the solid composition formed by theprocess of the present invention may be varied widely depending onfactors such as (a) the desired content of the active material in thesolid composition (b) the process used to obtain the solid product andthe desired properties of the aqueous film-forming medium and (c) thedesired properties (such as dispersibility) of the resultant solidcomposition.

Thus for example if the film-forming aqueous medium is to be used toform a cast tape or cast flakes, a relatively higher film-forming levelof polymer is likely to be required in the film-forming aqueous mediumas compared with the film-forming aqueous medium used for spray-drying.Similarly a more coherent product is likely required if the finalproduct is to be a cast tape rather than flakes. Such a coherent productis likely for example to require a relatively higher proportion offilm-forming polymer as compared with the solid filler content. Ingeneral, sufficient of the film-forming polymer should be used to form afilm-forming aqueous medium, by which is meant an aqueous medium havinga suitable rheology and in particular a suitable viscosity for thedrying process selected, for example for casting on a substrate. Ifthere is insufficient polymer in solution, the aqueous medium will tendto run off the substrate and form too thin a film. If on the other handtoo much polymer is present in the aqueous medium, it will not flowsmoothly and the resultant film will not be self-levelling and uniform.The optimum concentration of polymer to provide an effectivefilm-forming aqueous medium will vary depending on the exact nature andgrade of polymer used but may be determined by simple and routineexperimentation. Typical concentrations are illustrated in the Examples.Thus for example the concentration of the film-forming polymer in thefilm-forming aqueous medium typically from 0.5 to 95% by weight, forexample from 1 to 50% by weight. It will be appreciated however that oneskilled in the art may readily determine the optimum concentration offilm-forming polymer for any given process method.

As noted above, it is a particular advantage of the process of thepresent invention that a high loading of the water-soluble supportedmaterial may if desired be obtained in the solid composition. Forexample in favourable circumstances greater than about from 40% or 50%and even up to as high as 75% or more by weight of a water-solublesupported material such as an agrochemical active ingredient may beincorporated in the solid composition of the invention. This itselfcarries with it a further advantage in that potential problems of poordispersion of the solid composition in water may be greatly reduced whena major proportion of the solid composition is the water-solubleagrochemical. It may thus for example be possible to use a film-formingpolymer or other components which would otherwise give rise todispersion problems if used at higher concentrations or if used inconjunction with water-soluble insoluble components. It is of coursepossible to use lower proportions of water-soluble supported material,for example 20% or less by weight, if desired but some of the advantagesof the present invention may not be so apparent in such products.Furthermore, if an inorganic adjuvant such is ammonium sulphate is usedin conjunction with a water-soluble is agrochemical electrolyte, it ispossible to combine high loadings of the agrochemical electrolyte suchas a glyphosate salt with high loadings of ammonium sulphate, thusovercoming a severe stability problem which is commonly encountered whenglyphosate is used with ammonium sulphate in aqueous concentrates.

According to a further aspect of the present invention there is provideda solid, water-dispersible or water soluble composition comprising awater-soluble agrochemical electrolyte, a film-forming polymer which isa homopolymer or a partially charged block copolymer or a blockcopolymer capable of ring opening to form a partially charged blockcopolymer and a filler which is an ammonium salt.

According to a still further aspect of the present invention there isprovided a solid water-dispersible or water soluble compositioncomprising a glyphosate salt, an alkyl vinylether maleic acid copolymeror a hydrolysed derivative thereof and ammonium sulphate.

According to a still further aspect of the present invention there isprovided a solid water-dispersible or water soluble compositioncomprising ammonium glyphosate, methyl vinylether maleic acid copolymeror a hydrolysed derivative thereof and ammonium sulphate.

One skilled in the art will readily be able to determine appropriateproportions for each desired application but further detail is now givenfor the purposes of illustration only.

The proportion of polymer necessary to provide the required film-formingproperties of the aqueous medium depends, at least in part, on themolecular weight of the polymer. We have found for example that methylvinylether maleic acid copolymer having a number average molecularweight of from 20,000 to 990,000 for example a number average molecularweight of from 100,000 to 300,000 for example from about 200,000 toabout 250,000 is particularly suitable for the process of the presentinvention. If hydrolysed methyl vinylether maleic acid copolymer is usedas starting material, the molecular weight may be higher than that ofthe corresponding unhydrolysed precursor and number average molecularweights up to 3,000,000 may be used without detriment.

In general, we have found for example that for cast flake products, itis desirable to use a minimum of about 2% by weight of methyl vinylethermaleic acid anhydride or hydrolysed product thereof having a molecularweight of between about 100,000 and 300,000 to achieve coherent flakes.There is no real upper limit to the proportion methyl vinylether maleicacid anhydride which may be used but generally there is little advantagein a product having high levels of film-forming polymer and low levelsof supported material. The proportion of film-forming polymer in thefinal product is thus typically from 2% to 20% by weight.

We have found that surprisingly it is possible to use a non-absorptive,water soluble inorganic filler such as ammonium sulphate as filler inthe solid formulations. The upper limit of the proportion of inorganicsolid such as ammonium sulphate is generally determined by thebiological activating effect which it is desired to achieve and inparticular the desired glyphosate to ammonium sulphate ratio in thespray solution. There is little advantage in a product havingexcessively high levels of inorganic filler over and above that desiredto achieve the desired biological effect, and the proportion ofinorganic filler in the final product is thus typically from 1% to 90%by weight, for example from 2% to 50% by weight.

If desired, other components may be added to the film-forming aqueousmedium. Thus for example it may be desirable, particularly if the castproduct is to be a cast tape (a film), to include a plasticiser toimprove the flexibility of the cast product. Suitable plasticisersinclude glycerols, C₂ to C₆ glycols and polyglycols such as polyethyleneglycol, dialkyl phthalates such as dioctyl phthalate, sorbitol andtriethanolamine or mixtures thereof. In addition to improving theflexibility of the product a plasticiser may also have an advantageouseffect on the rate of dispersion of the dry, cast product in water. Theproportion of plasticiser is preferably within the range 0 to 80% byweight, for example from 5 to 30% by weight relative to the film-formingpolymer.

Surfactants may be added to the film-forming aqueous medium both toenhance the rate of dispersion of the dry product in water and also toaffect the surface tension properties of the film-forming aqueous mediumrelative to a substrate on which it is cast. Thus for example a wettermay be added to ensure wetting of the substrate, for example if aplastics substrate is used. If it is desired to produce cast tapesrather than flakes, surfactants may also be added which modify thesurface tension of the wet cast film and ensure that on drying the filmreduces in thickness with minimum shrinkage in the plane of thesubstrate on which it is cast. A wide variety of surfactants may be usedfor these purposes and suitable examples will occur to one skilled inthe art. Solid surfactants are generally preferred to liquid since theymay be present in relatively high loading in the cast product.

If the product is a solid formulation of an agrochemical electrolyte itwill generally be desirable to add a surfactant to provide adjuvantproperties in the final application, for example as a wetter orbiological enhancing agent. Very many adjuvants, for example adjuvantsenhancing biological activity, are know to those skilled in the art andin general conventional adjuvants may be incorporated in the process ofthe present invention without detriment. Typical adjuvants areillustrated in the Examples but the selection of such adjuvants does notform part of the present invention and many such may be used. It will beappreciated however that, as with any agrochemical formulation, not allconventional adjuvants will be compatible, particularly if used at highconcentration.

An antifoam agent may be added to prevent excessive aeration duringmixing of the film-forming aqueous medium. A viscosity aid may be addedif desired to modify the viscosity of the film-forming aqueous medium,for example to minimise any settling of the solid filler within thethickness of the wet film during drying. Suitable viscosity-modifyingaids include alginates, starch, gelatin, natural gums, hydroxyethylcellulose, methyl cellulose, silica and clays.

According to a further aspect of the present invention there is provideda solid water-soluble or water-dispersible composition whenever preparedby a method according to the present invention.

The film-forming polymer which is a partially charged homopolymer or apartially charged block copolymer or a homopolymer or block copolymercapable of ring-opening to form a partially charged-homopolymer or blockcopolymer and in particular the copolymer of methyl vinly ether/maleicanhydride or its hydrolysed or otherwise water-soluble derivative mayprovide additional advantageous effects in the aqueous spray solution.Such advantageous effects may include for example enhanced rainfastnessand reduced spray drift. Such beneficial effects will be achieved ofcourse whether the polymer is introduced as a result of the dissolutionof a solid composition of the present invention or otherwise. Thus forexample the polymer may be added directly to the aqueous spray solutioneither as a solid or more preferably as an aqueous solution or mayincluded in an aqueous concentrate intended for dilution prior to use.The introduction of spray-drift reducing or rainfastness enhancingpolymers has hitherto encountered compatibility problems, especiallywhen used in conjunction with electrolytes such as glyphosate andparaquat salts. Such compatibility problems which are acute in thefilm-forming compositions of the present invention are found even inmore dilute solutions.

Thus according to a further aspect of the present invention there isprovided an aqueous spray solution or an aqueous concentrate of anagrochemical electrolyte such as a glyphosate or paraquat saltcomprising a polymer which is a partially charged homopolymer or apartially charged block copolymer or a homopolymer or block copolymercapable of ring-opening to form a partially charged-homopolymer or blockcopolymer and in particular a copolymer of methyl vinly ether/maleicanhydride or its hydrolysed or otherwise water-soluble derivative.

The invention is illustrated by the following Examples in which allparts and percentages are by weight unless otherwise stated.

EXAMPLE 1

AGRIMIER VEMA AN-216 (0.5 g, a copolymer of methyl vinly ether/maleicanhydride having a number average molecular weight of about 216,000 to230,000; AGRIMER is a trade mark of ISP (Great Britain) Co. Ltd.) wasadded to ammonium glyphosate (9.0 g of an aqueous solution containing40% by weight glyphosate acid equivalent and a molar ratio of ammonia toglyphosate acid of 1.75:1), stirred manually and allowed to stand forapproximately 20 minutes until the polymer had dissolved. To thissolution, MERGITAL LM17 (1.2 g, C_(10/14) alcohol ethoxylate with 17moles EO, MERGITAL is a trademark of Henkel) and ammonium sulphate (4.3g, pre-ground to a fine powder using a mortar and pestle) were added.The resultant dispersion was mixed thoroughly over a period of 5 minutesuntil a homogenous, viscous slurry was produced.

The viscous film-forming medium was tape cast onto a polymer film(polythene) substrate using a “doctor blade” set at a blade height of 1mm. The cast tape was dried for 45 minutes in an oven maintained at 50°C. and then stripped from the substrate as a coherent sheet which wassubsequently subdivided into flakes.

The resultant solid contained 39.8% glyphosate salt (36.1% glyphosateacid equivalent), 5.0% copolymer, 12.0% Mergital LM17 and 43.2% ammoniumsulphate. The foregoing calculations are based on the assumption of anammonia:glyphosate ratio of 1:1 in the solid (over and above theammonium sulphate content). If this assumption is incorrect, the figuresare still indicative of the relative proportions in the solid.

When a sample of flakes (5.63 g) was exposed to ambient conditions (21°C. temperature, 66% relative humidity) in an open petri dish for 72hours, it did not deliquesce. The weight gain due to moisture pick-upunder these conditions was 1.6% in a sample which had been pre-dried for24 hours in an oven maintained at 50° C.

The dispersion time as measured by the standard test method given belowfor a 0.50 mm thick (0.22 g) sample was approximately 60 seconds.

The dispersion time of the solid was measured in a standard test bydropping a sample of between 4 and 10 flakes (of dimension 2 mm×2 mm)into a boiling tube (of approximate dimensions 8 inches×1 inch, with awater tight stopper) filled with tap water at 20° C.±1° C. to leave anullage space of 0.5 to 0.75 inches in the tube. The tube was invertedslowly such that the flakes are not allowed to sit on the bottom of thetube but are allowed to settle through the medium under the influence ofgravity. The time taken for the flakes to completely disperse was noted.

EXAMPLE 2

AGRIMER VEMA AN-216 (0.5 g) was added to ammonium glyphosate (9.0 g ofan aqueous solution containing 40% acid equivalent and an ammonia toglyphosate acid molar ratio of 1.75:1.00), stirred manually and allowedto stand for approximately 20 minutes until the polymer had dissolved.To this solution, ETHOMEEN T25 (1.2 g, Tallowamine ethoxylate with 15moles EO from Akzo Nobel Chemicals) and ammonium sulphate (4.3 g,pre-ground to a fine powder using a mortar and pestle) were added. Theresultant dispersion was mixed thoroughly over a period of 5 minutesuntil a homogenous, viscous slurry was produced.

The viscous film-forming medium was tape cast onto a polymer film(polythene) substrate using a “doctor blade” set at a blade height of 1mm. The cast tape was dried for 45 minutes in an oven maintained at 50°C. and then stripped from the substrate as a coherent sheet which wassubsequently subdivided into flakes.

The resultant solid contained 39.8% glyphosate salt (36.1% glyphosateacid equivalent), 5.0% copolymer, 12.0% ETHOMEEN T25 and 43.2% ammoniumsulphate.

When a sample of flakes (4.76 g) was exposed to ambient conditions (21°C. temperature, 66% relative humidity) in an open petri dish for 72hours, it did not deliquesce. The weight gain due to moisture pick-upunder these conditions was 1.5% in a sample which had been pre-dried for24 hours in an oven maintained at 50° C.

The dispersion time, as measured by the standard test method, for a 0.61mm thick (0.29 g) sample was approximately 93 seconds.

EXAMPLE 3

AGRIMER VEMA AN-216 (1.5 g) was added to ammonium glyphosate (22.5 g ofan aqueous solution containing 40% acid equivalent and a molar ratio ofammonia to glyphosate acid of 1.75:1.00), stirred manually and allowedto stand for approximately 20 minutes until the polymer had dissolved.To this solution, Mergital LM17 (3.0 g) and ammonium sulphate (10.5 g,pre-ground to a fine powder using a mortar and pestle) were added. Theresultant dispersion was mixed thoroughly over a period of 5 minutesuntil a homogenous, viscous slurry was produced.

The viscous film-forming medium was tape cast onto a polymer film(polythene) substrate using a “doctor blade” set at a blade height of 1mm. The cast tape was dried for 45 minutes in an oven maintained at 50°C. and then stripped from the substrate as a coherent sheet which wassubsequently subdivided into flakes.

The resultant solid contained 39.8% glyphosate salt (36.1% glyphosateacid equivalent), 6.0% copolymer, 12.0% Mergital LM17 and 42.2% ammoniumsulphate.

The solid was dissolved in water and the resultant solution showedexcellent bioefficacy when tested against standard plant species.

EXAMPLE 4

AGRIMER VEMA AN-216 (0.6 g), AEROSOL OT-B {0.2 g, sodiumdioctylsulphosuccinate (85%) and sodium benzoate (15%); AEROSOL is atrademark of American Cyanamid Company}, CALFLO E (3.0 g, a high surfacearea calcium silicate filler—CALFLO is a trademark of World Minerals)were added to ammonium glyphosate (22.0 g of an aqueous solutioncontaining 40% acid equivalent and an ammonia to glyphosate acid molarratio of 1.75:1.00), stirred manually and allowed to stand forapproximately 30 minutes until the polymer had dissolved. The resultantdispersion was mixed thoroughly over a period of 5 minutes until ahomogenous, viscous slurry was produced.

The viscous film-forming medium was tape cast onto a polymer film(polythene) substrate using a “doctor blade” set at a blade height of 1mm. The cast tape was dried for 45 minutes in an oven maintained at 50°C. and then stripped from the substrate as a coherent sheet which wassubsequently subdivided into flakes.

The resultant solid contained 71.8% glyphosate salt(65.3% glyphosateacid equivalent), 4.5% copolymer, 1.5% Aerosol OT-B and 22.2% CALFLO E.

When a sample of flakes (4.4 g) was exposed to ambient conditions(27-29° C. temperature, 35-57% relative humidity) in an open petri dishfor 24 hours, it did not deliquesce. The weight gain due to moisturepick-up under these conditions was 1.4% in a sample which had beenpre-dried for 24 hours in an oven maintained at 50° C.

The dispersion time, as measured by the standard test method, for a 0.40mm thick (0.34 g) sample was approximately 180 seconds.

EXAMPLE 5

Ammonium sulphate (2.8 g, pre-ground to a fine powder using a mortar andpestle) was added to ammonium glyphosate (22.0 g of an aqueous solutioncontaining 40% acid equivalent and an ammonia to glyphosate acid ratioof 1.75:1.00). AGRIMER VEMA AN-216 (1.0 g) and Aerosol OT-B (0.25 g)were then added and the dispersion stirred manually and allowed to standfor approximately 20 minutes until the polymer had dissolved. Theresultant dispersion was mixed thoroughly over a period of 5 minutesuntil a homogenous, viscous slurry was produced.

The viscous film-forming medium was tape cast onto a polymer film(polythene) substrate using a “doctor blade” set at a blade height of 1mm. The cast tape was dried for 45 minutes in an oven maintained at 50°C. and then stripped from the substrate as a coherent sheet which wassubsequently subdivided into flakes.

The resultant solid contained 70.5% glyphosate salt (64.1% glyphosateacid equivalent), 7.3% copolymer, 20.4% ammonium sulphate and 1.8%Aerosol OT-B.

When a sample of flakes (5.74 g) was exposed to ambient conditions (21°C. temperature, 66% relative humidity) in an open petri dish for 72hours, it did not deliquesce. The weight gain due to moisture pick-upunder these conditions was 4.5% in a sample which had been pre-dried for24 hours in an oven maintained at 50° C.

The dispersion time, as measured by the standard test method, for a 0.49mm thick (0.17 g) sample was approximately 48 seconds.

EXAMPLE 6

AGRIMER VEMA AN-216 (3.1 g) was added to ammonium glyphosate (51.2 g ofan aqueous solution containing 40% acid equivalent and an ammonia toglyphosate acid molar ratio of 1.75:1.00), stirred manually and allowedto stand for approximately 20 minutes until the polymer had dissolved.To this solution, Mergital LM17 (0.4 g) and ammonium sulphate (4.2 g,pre-ground to a fine powder using a mortar and pestle) were added. Theresultant dispersion was mixed thoroughly over a period of 5 minutesuntil a homogenous, viscous slurry was produced.

The viscous film-forming medium was tape cast onto a polymer film(polythene) substrate using a “doctor blade” set at a blade height of 1mm. The cast tape was dried for 45 minutes in an oven maintained at 50°C. and then stripped from the substrate as a coherent sheet which wassubsequently subdivided into flakes.

The resultant solid contained 74.5% glyphosate salt (67.7% glyphosateacid equivalent), 10.3% copolymer, 1.3% Mergital LM17 and 13.9% ammoniumsulphate.

The solid was dissolved in water and the resultant solution showedsatisfactory bioefficacy when tested against standard plant species.

EXAMPLE 7

Glyphosate trimesium (11.9 g of an aqueous solution containing 60.5%salt−41.7% glyphosate acid equivalent) was added to AGRIMER VEMA AN-216(1.2 g), stirred manually and allowed to stand for approximately 1 hour.To this solution, MERGITAL LM17 (2.4 g) and ammonium sulphate (7.6 g,pre-ground to a fine powder using a mortar and pestle) were added. Theresultant dispersion was mixed thoroughly over a period of 5 minutesuntil a homogenous, viscous slurry was produced.

The viscous film-forming medium was cast onto a polymer film (polythene)substrate using a “doctor blade” set at a blade height of 0.75 mm. Thecast tape was dried in an oven maintained at 70° C. and the solidstripped from the substrate as a strong, flexible tape.

The resultant solid contained 39.1% glyphosate salt (27.0% glyphosateacid equivalent), 6.5% copolymer, 13.1% Mergital LM17 and 41.3% ammoniumsulphate.

EXAMPLE 8

Potassium glyphosate (26.6 g of an aqueous solution containing 48.1% byweight of glyphosate acid equivalent and a molar ratio of potassium toglyphosate acid of 1.13:1), was added to AGRIMER VEMA AN-216 (1.5 g),stirred manually and allowed to stand for approximately 30 minutes. Tothis mixture, Aerosol OT-B (0.4 g) and ammonium sulphate (2.0 g,pre-ground to a fine powder using a mortar and pestle) were added. Theresultant dispersion was mixed thoroughly over a period of 5 minutesuntil a homogenous, viscous slurry was produced.

The viscous film-forming medium was cast onto a polymer film (polythene)substrate using a “doctor blade” set at a blade height of 0.75 mm. Thecast tape was dried in an oven maintained at 70° C. and the solidstripped from the substrate as a brittle tape.

The resultant solid contained 80.4% glyphosate salt (64.3% glyphosateacid equivalent), 7.5% copolymer, 2.0% Aerosol OT-B and 10.1% ammoniumsulphate.

EXAMPLE 9

Ammonium glyphosate (32.0 g of an aqueous solution comprising 45.0% byweight of glyphosate acid equivalent and a molar ratio of ammonia toglyphosate of 1.9:1) was added to a water soluble polymer (2.0 g) in a150 ml beaker and mixed using a mechanical stirrer, until the polymerdissolved/dispersed. To this solution/dispersion MORWET EFW (0.1 to 0.4g, a wetter consisting of an alkyl naphthalene sulphonate from Witco)and ammonium sulphate (20.4 g, preground to a fine powder using a mortarand pestle and sieved using a 0.5 mm sieve) were added. The resultantdispersion was mixed thoroughly for approximately 5 minutes and thehomogeneity of the slurry was observed. If ‘salting out’ had occurred,the slurry was discarded.

If a homogeneous slurry was obtained, the slurry was either cast using a“doctor blade” set at a blade height of 0.75 mm or poured and spreadonto a polymer film (polythene) substrate. The wet tape was dried in anoven maintained at 95° C. until it was strippable from the substrate asa dry solid. The resultant solid contains approximately 41% glyphosatesalt (37% glyphosate acid equivalent).

Flake thickness was measured using a micrometer screw gauge.

The dispersion time of the flakes was measured according to theprocedure described in Example 1. A dispersion of the flakes in waterwas filtered through a 150 micron sieve (typical of a sieve used inconnection with an agrochemical spray) and washed thoroughly in tapwater (18° C.±2° C.). The surface of the sieve examined visually forresidue.

Table 1 presents the results for the use of polymers according to thepresent invention whilst Table 2 presents comparative results when otherpolymers are used.

TABLE 1 Residue Flake Dispersion (150 Trade thickness Time micronPolymer Name (mm) (seconds) sieve) Copolymer of methyl AGRIMER 0.6-0.750 No vinyl ether/maleic VEMA anhydride with AN216 Average MW 216,000Acid form of above AGRIMER 2.5-4.0 45 No with Average VEMA MW 240,000H240 Acid form of above AGRIMER 0.5 49 No with Average VEMA H-2200 MW2,200,000 Poly(acrylic acid-co- 0.7-0.9 26 No maleic acid) sodium saltSulphonated polyvinyl GOHSERAN very soft 48 No alcohol, sodium saltL3266 Sulphenated poly- VERSA 0.6-0.9 90 No styrene, sodium salt TL502Co-polymer of VERSA TL3 0.5-0.6 40 No styrene/maleuc anhydridesulphonate, sodium salt Polyacrylic acid, 0.5-0.7 26 No sodium salt

TABLE 2 Residue Flake Dispersion (150 Trade thickness Time micronPolymer Name (mm) (seconds) sieve) Polyvinyl pyrrolidone AGRIMER 30“Salted — Out” Polyvinyl alcohol, “Salted — 88% hydrolysed Out”Quaternized AGRIMER “Salted — vinylpyrrolidone/ DAQ-2000 Out”dimethylaminoethyl methacrylate copolymer Copolymer of AGRIMER “Salted —vinylpyrrolidone/vinyl VA6 Out” acetate Hydroxyethyl cellulose 0.5 90Yes Carboxymethyl 2.0-3.0 300  Yes cellulose Polyethylenimine 0.7-0.8 61Yes Polyacrylamide brittle   300+  Yes Carrageenan Type 2 0.4 to 0.8 60Yes Alginic acid, 0.7 130  Yes sodium salt Carbohydrate, Starch PPE12590.6 120 Yes Xanthan gum KELZAN S 1.0-1.2 150 Yes

EXAMPLE 10

The procedure of Example 9 was repeated for AGRIMER VEMA AN216 with theexception that the amount of copolymer was increased from 2.0 g (5% w/w)to 8.0 g (20% w/w), and a corresponding decrease in ammonium sulphatecontent from 20.4 g to 14.4 g. Solid flakes of approximate thickness 0.7mm, was obtained. The flakes dispersed readily in water (Temp: 21° C.;dispersion time: 25 seconds) leaving no residue.

EXAMPLE 11

Ammonium glyphosate (32.0 g of an aqueous solution comprising 45.0% byweight of glyphosate acid equivalent and a molar ratio of ammonia toglyphosate of 1.9:1) was added to AGRIMER VEMA AN-216 (2.0 g) in a 150ml beaker and mixed using a mechanical stirrer, until the polymerdissolved/dispersed. To this solution/dispersion MORWET EFW (0.1 g, awetter consisting of an alkyl naphthalene sulphonate from Witco) andMergital LM17 (4.8 g) were added and mixed thoroughly using a mechanicalstirrer. The filler (15.9 g) was added to the above dispersion and mixedfor a further 5 minutes or until homogeneous.

The viscous film-forming medium was either cast using a “doctor blade”set at a blade height of 0.7 mm or poured and spread onto a polymer film(polythene) substrate. The wet tape was dried in an oven maintained at95° C. until it was strippable from the substrate as a dry solid. Theresultant solid contains approximately 41% glyphosate salt (37%glyphosate acid equivalent).

Flake thickness was measured using a micrometer screw gauge.

The dispersion time of the flakes was measured according to theprocedure described in Example 1. A dispersion of the flakes in waterwas filtered through a 150 micron sieve and washed thoroughly in tapwater (18° C.±2° C.) and the surface of the sieve examined visually forresidue. The results are presented in Table 3.

TABLE 3 Residue Flake Dispersion (150 Trade thickness Time micron FillerName (mm) (seconds) sieve) Ammonium sulphate 1.6-2.4 102  No Ammoniumhydrogen 1.6-1.8 88 No phosphate Micro talc 0.5-0.8 72 No Attpulgiteclay ATTAGEL 50 0.3-0.4 70 No Microtalc : 0.6-0.7 40 No Ammoniumsulphate (50 : 50)

EXAMPLE 12

Ammonium glyphosate (32.0 g of an aqueous solution comprising 45.0% byweight of glyphosate acid equivalent and a molar ratio of ammonia toglyphosate of 1.9:1) was added to AGRIMER VEMA AN-216 (2.0 g) in a 150ml beaker and mixed using a mechanical stirrer, until the polymerdissolved/dispersed. To this solution/dispersion MORWET EFW (0.1 g) andadjuvant (4.8 g) were added and mixed thoroughly using a mechanicalstirrer. Ammonium sulphate (15.9 g, preground to a fine powder using amortar and pestle) was added to the above dispersion and mixed for afurther 5 minutes or until homogeneous.

The viscous film-forming medium was either cast using a “doctor blade”set at a blade height of 0.75 mm or poured and spread onto a polymerfilm (polythene) substrate. The wet tape was dried in an oven maintainedat 95° C. until it was strippable from the substrate as a dry solid. Theresultant solid contains approximately 41% glyphosate salt (37%glyphosate acid equivalent).

Flake thickness was measured using a micrometer screw gauge.

The dispersion time of the flakes was measured according to theprocedure described in Example 1. A dispersion of the flakes in waterwas filtered through a 150 micron sieve and washed thoroughly in tapwater (18° C.±2° C.) and the surface of the sieve examined visually forresidue.

TABLE 4 Residue Flake Dispersion (150 Trade thickness Time micronAdjuvant Name (mm) (seconds) sieve) C_(10/14) alcohol MERGITAL 0.4-0.635 No ethoxylate with 17 LM17 moles EO Dimethylsiloxane SILWET 0.6-0.733 No glycol copolymer co-polymer L7500 Monobranched alcohol ATLOX MBA1.2-1.5 66 No ethoxylate 13/15 Tallowamine ETHOMEEN 0.6-0.7 91 Noethoxylate with 15 T25 moles EO

EXAMPLE 13

The procedure of Example 12 was repeated for Mergital LM17 with theexception that the amount of adjuvant was increased from 4.8 g (12.4%w/w) to 20.0 g (51.7% w/w), and a corresponding decrease in ammoniumsulphate content from 15.9 g to 0.7 g. Solid flakes of approximatethickness 0.31-0.5 mm, was obtained. The flakes dispersed readily inwater (Temp: 19° C.; dispersion time: 80 seconds) leaving no residue.

EXAMPLE 14

AGRIMER VEMA AN-216 (40 g) was added to ammonium glyphosate (600 g of anaqueous solution containing 40% acid equivalent; ammonia:glyphosateacid=1.75:1.00), stirred using a mechanical stirrer and allowed to standfor approximately 20 minutes until the polymer had dissolved. To thissolution, MERGITAL LM17 (80 g, C_(10/14) alcohol ethoxylate with 17moles EO, MERGITAL is a trademark of Henkel) and ammonium sulphate (280g, pre-ground to a fine powder using a mortar and pestle) were added.The resultant dispersion was mixed thoroughly until a homogenous,viscous slurry was produced.

The viscous slurry was then diluted with water until the rheology of theslurry was suitable for processing in a spray drier. The slurry wasspray-dried using disc atomisation in a Niro mobile minor. The inlettemperature was 160° C. and the outlet temperature was 60° C. Afilamentous solid was obtained.

EXAMPLE 15

Diquat dibromide concentrate (26 g, 23.06% w/w diquat ions) was added toAGRIMER VEMA AN-216 (2 g) and mixed until all the polymer had dissolved.MORWET EFW (0.2 g) and talc (2 g) and magnesium sulphate monohydrate (2g) were then added and mixed thoroughly until a homogenous slurry wasproduced.

The resultant slurry was then poured into a petri dish and placed in anoven maintained at a 50° C. A dry, water dispersible solid comprisingapproximately 34.5% diquat ions (64.4% diquat salt) was obtained.

1. A process for producing a solid, water-soluble or water-dispersible composition comprising a non film-forming material supported by a film-forming polymer wherein the supported material is a water-soluble material, which process comprises (i) preparing a film-forming aqueous medium containing (a) a film-forming polymer which is a partially or fully charged homopolymer or a partially charged block copolymer or a homopolymer or block copolymer capable of ring-opening to form a partially charged homopolymer or block copolymer and (b) a water soluble material which is non film-forming and thereafter (ii) drying the film-forming aqueous medium to form the solid composition, wherein the film-forming aqueous medium is prepared using water as the sole medium for both the film-forming polymer (a) and the water-soluble material (b) and wherein the film-forming polymer is selected from the group consisting of an alkyl vinylether maleic anhydride block co-polymer, a hydrolysed alkyl vinylether maleic anhydride block co-polymer, a salt of poly (acrylic acid/maleic acid) copolymer, a salt of sulphonated poly (styrene/maleic anhydride) copolymer, a salt of sulphonated polystyrene and a salt of sulphonated polyvinyl alcohol.
 2. A process according to claim 1 wherein the water soluble material which is non film-forming is a salt of glyphosate, a bipyridylium salt, glufosinate, fomesafen or ammonium sulphate.
 3. A process according to claim 1 wherein the film-forming polymer is an alkyl vinylether maleic anhydride block co-polymer having a number average molecular weight of from 20,000 to 990,000 or is a hydrolysed alkyl vinylether maleic anhydride block co-polymer having a molecular weight from 20,000 to 3,000,000.
 4. A process according to claim 1 wherein the water-soluble material is a salt of glyphosate, the film-forming medium is an alkyl vinylether maleic anhydride co-polymer and there is incorporated in the film-forming medium an ammonium salt in the substantial absence of an inert filler.
 5. A process according to claim 1 wherein there is included an inert inorganic filler.
 6. A process according to claim 1 wherein the concentration of the film-forming polymer in the film-forming aqueous medium is from 0.5 to 96% by weight.
 7. A process according to claim 1 wherein the content of the water soluble supported material in the solid composition of the invention is greater than 40% by weight.
 8. A solid, water-soluble or water-dispersible composition comprising a glyphosate salt, an alkyl vinylether maleic anhydride block co-polymer or a hydrolysed derivative thereof and ammonium sulphate. 